[Amps] SB220 running plate current when no drive

[Alek Petkovic]

Grid to filament short in one or both tubes.

73, Alek, VK6APK

On 6/10/2020 2:03 am, Steve AA7V wrote:
> Hello to the group;
>
> My SB220 has started to act up.
>
> Immediately upon power on, the 3-500s both start drawing plate current. The
> meter shows approximately 250 ma of current. It is apparent some component
> has failed.
>
> Also, it appears the grid current meter is showing a negative value (if
> this is possible) as the needle now rests on the left peg.
>
> I am not adverse to troubleshooting to the component level but would
> appreciate any advice as to how to narrow my search to a specific set of
> probable causes.
>
> If I am unable to fix this amp, does anyone have any recommendations
> towards a person that works on SB220s?
>
> Regards
>
> Steve AA7V
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